http://www.citrix.com/English/ps2/products/feature.asp?contentID=1686939
Obviously, this step is taken in order to battle VMware and its free ESXi server.
Compared by the XenServer vs. ESXi feature set, Citrix offers enterprise level technology such as Live Migration (Xen Motion compared to VMotion for ESX) and many others features for free. Also, Xen is teaming up with Microsoft on Hyper-V in deploying Virtualization Management software.
But VMware is also teaming up with Cisco (Fibre Channel over Ethernet, Unified IO Nexus Hardware ), Emulex (Fibre Channel over Ethernet Host Bus Adapters, CNA ) and EMC²
Last week I attended a presentation event by VMware and its peers (Cisco, Emulex, EMC²) and we can expect quite a few cool features & technology to come.